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United States Patent | 5,529,520 |
Iwashita ,   et al. | June 25, 1996 |
A propulsion unit for watercraft that employs a pair of counter-rotating propellers disposed one in front of the other in order to improve the performance upon acceleration, a cavitation effect is generated around at least one of the propellers at least during acceleration. Various ways in which this can be done employing the exhaust gases from the powering internal combustion engine for driving the propellers are illustrated.
Inventors: | Iwashita; Takashi (Hamamatsu, JP); Iriono; Yasushi (Hamamatsu, JP); Sumino; Yoshitugu (Hamamatsu, JP); Harada; Hiroshi (Hamamatsu, JP) |
Assignee: | Sanshin Kogyo Kabushiki Kaisha (Hamamatsu, JP) |
Appl. No.: | 318056 |
Filed: | October 4, 1994 |
Oct 04, 1993[JP] | 5-271255 |
Current U.S. Class: | 440/66; 440/80; 440/900 |
Intern'l Class: | B63H 005/10 |
Field of Search: | 440/900,88,89,79-81,66 416/909,93 R,93 A,146 R,146 B 60/310 |
3434447 | Mar., 1969 | Christensen et al. | 440/89. |
4871334 | Oct., 1989 | McCormick | 440/89. |
4911665 | Mar., 1990 | Hetzel | 440/89. |
Foreign Patent Documents | |||
0103792 | May., 1988 | JP | 440/80. |